National Mourning Day is observed in Panama every December 20 to commemorate the events of December 20, 1989, when the United States conducted Operation Just Cause, resulting in the invasion of Panama. This operation aimed to depose the Panamanian leader Manuel Noriega and install President-elect Guillermo Endara. The day is marked by memorial ceremonies where authorities, military personnel, and civilians lay flowers and wreaths at monuments dedicated to the victims of the U.S. aggression. The estimated casualties during the operation vary, with figures ranging from 500 to 3,000 deaths, highlighting the complexity of the event's legacy. The observance serves as a solemn reminder of the impact of foreign intervention on the nation.